FIELD OF THE INVENTION AND RELATED ART
[0001] The present invention relates to a data recording medium having a recording layer
comprising a polymer liquid crystal. More specifically, the present invention relates
to a data recording medium having a recording layer comprising a polymer liquid crystal,
suitable for use in an optical recording and reproduction apparatus and in the form
of a disk, a tape and a card format.
[0002] In recent years, research and development of rewritable recording media for use as
a large capacity memory, a display, etc., have been extensively made. One of such
media has been known to utilize phase transition of a liquid crystal.
[0003] For example, a layer of aligned liquid crystal sandwiched between a pair of transparent
electrodes or appropriate substrates is optically transparent. If the liquid crystal
layer is raised to a temperature above a phase transition temperature (of nematic
phase → isotropic phase, or smectic phase → nematic phase) and then suddenly cooled,
the liquid crystal layer is not restored to the original transparent state but assumes
a light-scattering state. Thus, the resultant contrast can be used for recording and
readout. After the writing, the restoration of the liquid crystal phase such as smectic
phase is caused by applying an electric field between the electrodes or by heating
and gradually cooling the recording medium, thereby to effect erasure. Further, heating
with or without voltage application can be used for erasure.
[0004] On the other hand, a polymer liquid crystal having a glass transition temperature
and an excellent memory characteristic has been recently calling attention. Ordinally,
for the heating of a polymer liquid crystal layer, a semiconductor laser which is
compact and inexpensive has been frequently used. The oscillation wavelength available
by the laser is generally 650 nm or longer, and the laser light power is smaller than
that of a gas laser, such as argon laser or helium-neon laser. As an ordinary liquid
crystal does not show an absorptivity in such a near infrared region, it has been
proposed to incorporate a light-absorbing dye in a liquid crystal layer.
[0005] However, a dye showing an absorptivity in the near infrared region is generally not
sufficiently thermally stable in a liquid crystal medium, so that it is partially
decomposed during repetition of writing-erasure until the recording medium fails to
provide a sufficient contrast.
[0006] In view of the above problem, it has been proposed to cause light absorption by providing
a light absorbing layer of phthalocyanine which is a very stable pigment or dispersing
phthalocyanine in a polymer liquid crystal (Japanese Laid-Open Patent Application
JP-A (Tokkai) Sho 60-179294).
[0007] However, the provision of a light-absorbing layer or dispersion of a pigment in the
recording layer causes a lowering in efficiency of light absorption for heat generation.
The dispersion for recording at minute pits on the order of 1 µm causes undesirable
lowering in S/N ratio or scattering by the particles.
[0008] As a solution to the above problems, it has been tried to dissolve a stable pigment
such as phthalocyanine and reported to dissolve such a pigment in a low-molecular
weight liquid crystal, thus showing a possibility of improving the durability of an
optical recording system using a low-molecular weight liquid crystal (Japanese Laid-Open
Patent Application JP-A (Tokkai) Sho 62-25191).
[0009] In addition, while not with respect to a recording medium using a low-molecular weight
or polymer liquid crystal, a chemical combination of a polymer and a pigment has been
reported as a method for solubilizing a stable pigment (JP-A (Tokkai) Sho 61-232448).
[0010] However, in the above-mentioned rewritable data recording media utilizing optical
absorption other than one using a recording layer of a polymer liquid crystal and
structural fixation by utilizing its phase transition, melting point or glass transition
point, the recording layer per se is liable to be degraded, and the recording, reproduction
and erasure are liable to be unstable chemically or physically. Further, the contrast
in the recording state is low so that the detection and reproduction system may become
complicated.
[0011] In contrast thereto, a data recording medium having a recording layer comprising
a polymer liquid crystal shows an excellent stability and a high contrast, but it
requires that a light absorbent is dissolved in a polymer liquid crystal at a substantially
molecular level in as large a quantity as possible.
[0012] However, colorants or pigments conventionally dissolved in a polymer liquid crystal
either have a low solubility in the polymer liquid crystal or remarkably lower the
melting point or glass transition point of the resultant liquid crystal phase even
if it is dissolved. Further, the liquid crystal phase is liable to be unstabilized
or caused to have a lower clearing point so as to have the liquid crystal phase disappear
frequently.
[0013] The EP-A-0 140 133 describes polymers containing groups which are able to produce
discoatic liquid crystals. In specific examples of this document, phthalocyanine is
used.
[0014] For the above problems, it has been difficult to compatibly provide both a high light-absorption
efficiency and a stable recording state by the addition of a light absorbent.
SUMMARY OF THE INVENTION
[0015] Accordingly, an object of the present invention is to provide a data recording medium
having a recording layer which comprises a polymer liquid crystal and an additive
showing an absorptivity to wavelengths in the near infrared region and stably dissolved
in the polymer liquid crystal and is free from degradation on repetition of a writing-erasure
cycle.
[0016] Another object of the present invention is to provide a data recording medium having
a recording layer comprising a polymer liquid crystal, which is excellent in reversibility,
capable of recording a large optical density difference, capable of essentially stable
recording through utilization of the phase transition, melting point or glass transition
point of the polymer liquid crystal, and yet capable of realizing stable and sufficient
light-absorptivity without causing a lowering in glass transition point or unstabilization
of the liquid crystal phase.
[0017] According to the present invention, there is provided a data recording medium having
a recording layer which comprises a polymer liquid crystal and a colorant being soluble
in said polymer liquid crystal and being naphthalocyanine which is inclusively represented
by the following Formula (I) :
wherein the symbols A, B, C and D respectively denote the following divalent group:
wherein R
1 - R
12 respectively denote a hydrogen group, a linear or branched alkyl, alkoxy or alkenyl
group having 4 to 20 carbon atoms, or a group selected from the following: -SiQ
1Q
2Q
3, -SQ
4, -COQ
5, COOQ
6, and -NQ
7Q
8, wherein Q
1 - Q
8 respectively denote a hydrogen atom, or a linear or branched alkyl or alkenyl group
having 1 to 20 carbon atoms;
M denotes Ge, Sn, transition metal, Al, Ga, In, alkaline earth metal, lanthanide element
or actinide element, or an oxide, halogenide or alkoxide thereof.
[0018] Preferably, said colorant is a naphthalocyanine represented by the following Formula
(II):
wherein M denotes M denotes Ge, Sn, transition metal, Al, Ga, In, alkaline earth metal,
lanthanide element or actinide element;
X denotes halogen atom, alkyl group, carboxyl group, alkoxy group, ether group or
alkenyl group;
Xm1 - Xm4 respectively denote halogen atom, alkyl group, sulfomoyl group, ether group or alkenyl
group;
a - d are respectively a number of 0 to 4 satisfying the relationship of a+b+c+d ≥
1.
[0019] These and other objects, features and advantages of the present invention will become
more apparent upon a consideration of the following description of the preferred embodiments
of the present invention taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
Figures 1 and 2 are respectively a schematic sectional view showing an embodiment
of the data recording medium of the present invention;
Figure 3 is an illustration of an apparatus system for recording, reproduction and
erasure on the data recording medium of the present invention; and
Figure 4 is a phase diagram of a polymer liquid crystal composition used in the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] In addition to the aforementioned soluble colorant, the recording layer may further
comprise a metal chelate being different from the specified colorant.
[0022] Examples of such a metal chelate compound may include those represented by the following
formulas (1) - (17) :
wherein R
15 denotes a hydrogen atom, hydroxyl group or alkyl group capable of being connected
with another R
15; R
16 denotes alkyl group, halogen atom, hydrogen atom, nitro group, or benzo condensed
group; and M denotes a center metal of Cu, Ni, Co or Pd.
wherein R
17 denotes a hydrogen atom, hydroxyl group, alkyl group or aryl group capable of being
connected with another R
17; R
18 denotes a halogen atom, alkyl group, nitro group or condensed benzo group; and M
denotes Cu, Ni, Co or Pd.
wherein R
19 denotes an alkyl group or aryl group; R
20 denotes a hydrogen atom, halogen atom, alkyl group, aryl group, nitro group or condensed
benzo group; and M denotes Cu, Ni or Pd.
wherein R
21 denotes an alkyl group or aryl group; R
22 denotes a hydrogen atom, halogen atom, alkyl group or condensed benzo group; and
M denotes Cu, Ni or Pd.
wherein R
23 denotes a hydrogen atom or alkyl group; and M denotes Cu or Ni.
wherein R
24 denotes a hydrogen atom or alkyl group; and M denotes Cu, Ni, Co or Mn.
wherein R
25 and R
26 respectively denote a substituted or non-substituted alkyl group, acyl group or aryl
group and R
25 and R
26 are capable of forming an aromatic ring in combination; M denotes Cu, Ni, Co or Pd
which can have a charge and a counter ion.
wherein R
27 denotes a sulfur atom, substituted or non-substituted amino group, oxygen atom or
thioketone group; R
28 denotes a hydrogen atom, alkyl group, halogen atom or amino group; and M denotes
Zn, Cu or Ni.
wherein R
29 denotes an alkyl group, aryl group or styryl group; and M denotes Cu, Ni or Co.
wherein R
30 denotes a hydrogen atom, halogen atom, alkyl group, acyl group or aryl group; X is
optional and may denote Cl and M denotes Ni or Zr.
wherein R
31 denotes an alkyl group or aryl group; and M denotes Cu, Ni or Co.
wherein R
32 and R
33 respectively denote an alkyl group or aryl group; and M denotes Ni.
wherein R
34 and R
35 respectively denote an alkyl group, amino group, aryl group or furan group capable
forming an alicyclic ring in combination with each other; and M denotes Ni.
wherein R
36 and R
37 denote a hydrogen atom, halogen atom or alkyl group; X denotes an oxygen atom or
sulfur atom; and M denotes Ni.
wherein R
38 and R
39 respectively denote a hydrogen atom, alkyl group, halogen atom or nitro group; X
denotes an oxygen atom or sulfur atom; M denotes Ni; and Y
⊕ denotes a quarternary ammonium cation.
wherein R
40 denotes an amino group; and M denotes Cu, Ni, Co or Pd.
wherein R
41 denotes a hydrogen atom, halogen atom, alkyl group, acyl group, nitro group or alkoxyl
group; and M denotes Zn, Cu, Ni or Co.
[0024] The above-mentioned metal chelate compounds may be synthesized according to methods
as disclosed by Hurry B. Gray, Journal of the Am. Chem. Soc., vol. 88, pp 43-50 or
by Shlantz and Mybake, Journal of the Am. Chem. Soc., vol. 87, pp 1483-1489.
[0025] The above metal chelate compounds show an absorptivity in the near infrared region,
are useful as stable light-absorbing colorants and further have good mutual solubility
with or dispersibility in a polymer liquid crystal. Some metal chelate compounds among
them show dichroism, and a thermally stable guest-host type memory or display device
can be obtained by mixing such a compound showing dichroism within a polymer liquid
crystal. It is possible to incorporate two or more species of the metal chelate compound
in a polymer liquid crystal.
[0026] The metal chelate compound may be added in a proportion of 0.01 - 10 wt. %, preferably
0.05 - 5 wt. %, of the liquid crystal.
[0027] In combination with the above metal chelate compound, it is possible to use another
near-infrared absorbing colorant or dichroic colorant. Representative examples of
such near-infrared absorbing colorants may include cyanine, merocyanine, phthalocyanine,
tetrahydrocholine, dioxazine, anthraquinone, tripheno-dithiazine, xanthene, triphenylmethane,
pyrylium, croconium, azulene and triphenylamine. These colorants can be added in a
proportion of 0.01 to 10 wt. % of the polymer liquid crystal so as not to give ill
effects to the glass transition point or melting point of the polymer liquid crystal.
[0028] As additive for enhancing absorptivity in the near-infrared region used in the present
invention, the specific soluble colorant of formula (I) is added in addition to the
polymer liquid crystal.
[0029] It has been generally known that a colorant having a bar shape similarly as a liquid
crystal molecule has a good solubility in a liquid crystal and does not hinder the
liquid crystal phase. However, such a bar-shaped colorant soluble in a liquid crystal
generally has a low molecular weight and remarkably lowers the melting point or glass
transition point of a polymer liquid crystal when added to the latter.
[0030] According to our investigation, it has been found that a soluble organic large cyclic
colorant having a planar or plate-like shape instead of a bar shape and having 10
or more carbon atoms, preferably 20 or more carbon atoms, not only has an excellent
durability in resistance to the repetition of an optical recording process including
recording, reproduction and erasure but also shows good solubility because of its
shape in a polymer liquid crystal, to thereby provide a high absorptivity, good S/N
ratio and low bit error rate (BER). Further, it has been also found that such a large
cyclic colorant, because of its two-dimensional extension, does not hinder the liquid
crystal characteristic of a polymer liquid crystal nor does it result in an increased
mobility which leads to a remarkable lowering in clear point (T
Cl), glass transition point (Tg) and melting point.
[0031] The large cyclic colorants to be used for the present invention include naphthalocyanines
represented by the following formula (I), some of which may also be classified as
metal chelate compounds:
wherein the symbols A, B, C and D respectively denote the following divalent group:
wherein R
1 to R
12 respectively denote a hydrogen group, a linear or branched alkyl, alkoxy or alkenyl
group having 4 - 20 carbon atoms, or a group selected from the following:
-SiQ
1Q
2Q
3, -SQ
4, -COQ
5, COOQ
6 and -NQ
7Q
8, wherein Q
1 - Q
8 respectively denote a hydrogen atom, or a linear or branched alkyl or alkenyl group
having 1 - 20 carbon atoms;
M denotes Ge, Sn, transition metal, Al, Ga, In, alkaline earth metal, lanthanide element
or actinide element, or an oxide, halogenide or alkoxide thereof.
[0032] It is particularly important to use a semiconductor laser having a wavelength in
the region of near infrared to visible red from the view point of the campactness
and high performance of a recording and reproduction apparatus. As soluble organic
large cyclic colorants showing an absorptivity in the wavelength region, naphthalocyanines
are particularly preferred, among which those represented by the following formula
(II) are particularly suitable for the recording medium of the present invention because
of excellent solubility thereof.
wherein M denotes Ge, Sn, transition metal, Al, Ga, In, alkaline earth metal, lanthanide
element or actinide element; X denotes halogen atom, alkyl group, carboxyl group,
alkoxy group, ether group or alkenyl group; Xm
1 - Xm
4 respectively denote halogen atom, alkyl group, sulfamoyl group, ether group or alkenyl
group; a - d are respectively a number of 0 - 4 satisfying the relationship of a+b+c+d
≧ 1.
[0033] These compounds may be easily prepared, for example, by a method disclosed in Japanese
Laid-Open Patent Application JP-A (Kokai) Sho 62-90291.
[0034] The soluble organic large cyclic colorant may be added to a polymer liquid crystal
in a proportion of 0.01 - 40 wt. %, preferably 0.1 - 25 wt. %, of the latter.
[0035] The organic large cyclic colorant can be used in combination with another near-infrared-absorbing
colorant or dichroic colorant, examples of which may include cyanine, merocyanine,
naphthoquinone, tetra-hydrocholine, dioxazine, anthraquinone, tripheno-dithiazine,
xanthene, triphenylmethane pyrylium, croconium, azulene, triphenylamine, and metal
chelate compound. These additional colorants can be added in a proportion of ordinarily
0.01 - 10 wt. %, preferably 0.01 - 2 wt. %, of the polymer liquid crystal so as not
to give ill effects to the glass transition point or melting point of the polymer
liquid crystal.
[0036] In addition, it is possible to add an ultraviolet absorber, antioxidant or low-molecular
weight liquid crystal within an extent of not giving ill effects to the glass transition
point or melting point of the polymer liquid crystal.
[0037] The polymer liquid crystal used in the present invention is a thermotropic one, of
which a mesomorphic phase of nematic, smectic, chiral smectic, cholesteric or discotic
phase is utilized.
[0039] In the present invention, it is possible to use a mixture of a plurality of different
polymer liquid crystals. It is also possible to use a mixture of a polymer liquid
crystal and a low-molecular weight liquid crystal. In such a case, it is preferred
to restrict the amount of the low-molecular weight liquid crystal to 10 parts by weight
or less with respect to 1 part by weight of the polymer liquid crystal. For this purpose,
an ordinary low-molecular weight liquid crystal may be used without any restriction.
Herein, the term "low-molecular weight (or non-polymeric) liquid crystal" is used
in contrast with the term polymer liquid crystal and refers to a liquid crystal or
mesomorphic compound which is substantially free of repetition of a mesogen unit and
has two recurring mesogen units at the maximum, if any. The term "polymer liquid crystal"
used herein refers to a liquid crystal or mesomorphic compound having a number of
recurring units of 5 or more, preferably 10 or more.
[0040] It is also possible to use a ferroelectric liquid crystal having a chiral asymmetric
carbon atom which can be used alone or compatibly mixed with a polymer liquid crystal
as enumerated above to provide a ferroelectric polymer liquid crystal composition.
[0041] It is further possible as desired to incorporate in the recording layer comprising
the above mentioned polymer liquid crystal an ordinary polymer, such as olefin type
resin, acrylic resin, polystyrene resin, polyester resin, polyurethane resin, or polycarbonate
resin; an oligomer, an antioxidant, a plasticizer, an ultraviolet absorber, a quencher,
etc.
[0042] The polymer liquid crystal or its composition may be formed into a recording layer
in the form of a film by coating a substrate with a solution of the polymer liquid
crystal in an appropriate solvent by spin coating, dipping etc., followed by drying;
by sandwiching a polymer liquid crystal with a pair of substrates followed by pressing
under heating; or by using a film of a polymer liquid crystal prepared in advance.
The recording layer of a polymer liquid crystal may preferably have a thickness in
the range of 0.01 - 100 µm.
[0043] In the case of effecting recording and erasure through utilization of transition
between liquid crystal phase and isotropic phase and fixing of the resultant states
by using a glass transition point, a recording layer containing a polymer liquid crystal
need not be subjected to an aligning treatment but can be simply formed by application
of a polymer liquid crystal composition as described above.
[0044] On the other hand, a generally known orientation treatment can be applied in order
to effect uniform alignment of the polymer liquid crystal in a particular direction.
Such known orientation methods may include, stretching, rubbing, oblique vapor deposition,
application of a shearing force to a polymer liquid crystal sandwiched between a pair
of substrates, gradual phase transition under application of a magnetic field, and
orientation by using spacer edges.
[0045] Figures 1 and 2 are respectively a schematic sectional view showing an embodiment
of the data recording medium according to the present invention. A data recording
medium shown in Figure 1 comprises a pair of substrates 1a and 1b having thereon alignment
control films 2a and 2b, respectively, a recording layer 3 according to the present
invention disposed between the substrates 1a and 1b, and a reflection layer 4. Further,
a data recording medium shown in Figure 2 comprises members 1a, 1b, 2a, 2b and 3 which
are similar to those denoted by the corresponding numerals in Figure 1, and a transparent
electrode 5 and an electrode and reflection layer 6.
[0046] Figure 3 shows an outline of a system for illuminating such a data recording medium
10 with a laser beam to effect writing and readout. Referring to Figure 3, for the
recording, a laser beam emitted from a semiconductor laser 8 as a laser oscillator
is focused through optical systems 11 and a reflection mirror 12 to be incident on
the recording medium 10.
[0047] For the readout, a laser beam emitted from the semiconductor laser 8 is passed through
the optical systems 11 the polarizer 13, a beam splitter 7 and the reflection mirror
12 to illuminate the recording medium 10, and the reflected light from the recording
medium 10 is again passed through the beam splitter 7 and an analyzer 14 to be detected
by an optical detector 9.
[0048] Hereinbelow, the present invention will be explained in more detail with reference
to Examples.
Reference Example
[0049] A glass substrate in the form of a disk with a diameter of 130 mm and a thickness
of 1.2 mm was coated with a polyamic acid solution ("PIQ" (trade name), mfd. by Hitachi
Kasei Kogyo K.K.), followed by heating and rubbing, to be provided with a polyimide
alignment film.
[0050] On the polyimide film, the following side chain-type polymer liquid crystal and a
metal chelate compound (Compound No. 3 in the above Table 1) in a proportion of 0.15
wt. % of the liquid crystal were mixed with 1,1,2-trichloroethane and applied by spinner
coating, followed by drying, to form a 3 µm-thick recording layer.
[0051] Separately, a glass substrate coated with a reflection film (vapor-deposited aluminum
film) was provided with a polyimide alignment film similarly as above and superposed
on the recording layer of the polymer liquid crystal by the medium of a 3 µm-thick
spacer disposed at the periphery. A partial section of the thus formed laminate is
shown in Figure 1. The above laminate was heated to 90°C and gradually cooled to provide
the liquid crystal layer with a nematic phase, whereby a data recording medium was
prepared.
[0052] As shown in Figure 3, the recording medium was irradiated from its transparent substrate
side with a laser beam of 830 nm from a semiconductor laser 8 at a recording power
of 3.0 mW, whereby the irradiated part caused an alignment disorder to form a scattering
state. Then, the thus formed record was reproduced by illumination at a readout power
of 0.3 mW. The reflected light was detected by the optical detector 9 to provide a
reproduction contrast ratio (= |A-B|/A; A and B: signal intensities from non-recorded
and recorded portions, respectively).
[0053] The recording medium after the recording was subjected to an erasure operation comprising
heating to 90°C followed by gradual cooling to cause realignment of the recorded portion.
[0054] The above recording and erasure operations were repeated in 300 cycles, and the recording
medium after the 300 cycles of the recording and erasure (more exactly, after recording)
was subjected to the above reproduction operation to measure a reproduction contrast
ratio as described above.
Example 1
[0055] The following polymer liquid crystal and soluble naphthalocyanine ("IRD 1001", mfd.
by Yamamoto Gosei K.K.) were mixed in various proportions, followed by removal of
the solvent by evaporation under a reduced pressure to form a series of polymer liquid
crystal compositions.
[0056] Figure 4 is a phase diagram showing the phase transition characteristics of the above-prepared
polymer liquid crystal compositions confirmed by DSC (differential scanning calorimetry)
and microscopic observation. As shown in Figure 4, the above series of polymer liquid
crystal compositions showed a stable liquid crystal phase even at a colorant concentration
of 20 wt. % or above and the glass transition temperatures thereof were stable in
the range of 30 - 70°C.
Example 2
[0057] A glass substrate in the form of a disk with a diameter of 130 mm and a thickness
of 1.2 mm was coated with a polyamic acid solution ("PIQ" (trade name), mfd. by Hitachi
Kasei Kogyo K.K.), followed by heating and rubbing, to be provided with a polyimide
alignment film.
[0058] On the polyimide film, 10 wt. parts of the following side chain-type polymer liquid
crystal and soluble naphthalocyanine ("IRD 1001", Yamamoto Gosei K.K.) in a proportion
of 5.0 wt. % of the liquid crystal were mixed with 100 wt. parts of 1,1,2-trichloroethane
and applied by spinner coating, followed by drying, to form a 1 µm-thick polymer liquid
crystal layer.
[0059] The polymer liquid crystal composition showed Tg (glass transition temperature) =
35°C and T
Cl (nematic-isotropic transition temperature) = 75°C. The T
Cl is not substantially different from and the Tg is slightly lower than those of the
polymer liquid crystal alone. The liquid crystal composition also showed a good liquid
crystal temperature range.
[0060] Separately, a glass substrate coated with a reflection film (vapor-deposited aluminum
film) was provided with a polyimide alignment film similarly as above and superposed
on the recording layer of the polymer liquid crystal by the medium of a 1 µm-thick
spacer disposed at the periphery. A partial section of the thus formed laminate is
shown in Figure 1. The above laminate was heated to 90°C and gradually cooled to provide
the liquid crystal layer with a nematic phase, whereby a data recording medium was
prepared.
[0061] As shown in Figure 3, the recording medium was irradiated from its transparent substrate
side with a laser beam of 830 nm from a semiconductor laser 8 at a recording power
of 3.0 mW, whereby the irradiated part caused an alignment disorder to form a scattering
state. Then, the thus formed record was reproduced by illumination at a readout power
of 0.3 mW. The reflected light was detected by the optical detector 9 to provide a
reproduction contrast ratio (= |A-B|/A; A and B: signal intensities from non-recorded
and recorded portions, respectively).
[0062] The recording medium after the recording was subjected to an erasure operation comprising
heating to 90°C followed by gradual cooling to cause realignment of the recorded portion.
[0063] The above recording and erasure operations were repeated in 300 cycles, and the recording
medium after the 300 cycles of the recording and erasure (more exactly, after recording)
was subjected to the above reproduction operation to measure a reproduction contrast
ratio as described above.
[0064] As a result, reproduction contrast ratio of 0.4 was obtained at the initial stage,
and a reproduction contrast of 0.39 was obtained, thus showing a good durability.
No difference in Tg or T
Cl was observed either.
Comparative Example 1
[0065] A data recording medium was prepared and evaluated in the same manner as in Example
2 except that the metal chelate compound mixed with the polymer liquid crystal was
replaced by the following colorant in an amount of 5 wt. % of the polymer liquid crystal.
[0066] The resultant composition showed no liquid crystal phase at all.
Comparative Example 2
[0067] A glass substrate of 130 mm diameter and 1.2 mm thick provided with a transparent
electrode layer of vapor deposited ITO was coated with a polyamic acid solution ("PIQ",
Hitachi Kasei Kogyo K.K.), followed by heating and rubbing, to form a polyimide alignment
film.
[0068] On the polyimide film, 10 wt. parts of the following polymer liquid crystal and 0.3
wt. part of soluble phthalocyanine were dissolved in 100 wt. parts of 1,1,2-trichloroethane
and applied by spinner coating, followed by drying, to form a 3 µm-thick liquid crystal
layer:
[0069] Separately, a glass substrate coated with an electrode and reflection layer (vapor-deposited
aluminum film) was provided with a polyimide alignment film similarly as above and
superposed similarly as in the Reference Example on the above-prepared liquid crystal
recording layer by the medium of a 3 µm-thick spacer. A partial section of the thus
formed laminate is shown in Figure 2.
[0070] The above laminate was heated to 90°C and gradually cooled to have the liquid crystal
layer assume a uniaxially aligned smectic phase. Under this state, an electric field
of 5 V/µm was applied between the electrodes to uniformize the polarization direction,
whereby a data recording medium was prepared.
[0071] The recording layer of the recording medium thus prepared was supplied with a reverse
electric field of 5 V/µm between the transparent electrode (ITO) and the Al electrode
and simultaneously irradiated from the transparent electrode side with a semiconductor
laser beam of 830 nm at a recording power of 3.0 mW, whereby the irradiated part was
heated to cause an inversion of the spontaneous polarization, so that recording was
effected.
[0072] Then, the thus recorded recording medium was illuminated with a laser light at a
reproduction power of 0.3 mW in the absence of an electric field and the reflected
light containing differences in birefringence due to differences in polarization direction
was incident to an optical detector to measure a reproduction contrast ratio of 0.4
(= |A-B|/A, A and B: reflected light intensities from recorded and non-recorded portions,
respectively).
[0073] The whole area or the recorded portion of the recording layer after the recording
was irradiated with a laser light at a power of 3.5 mW while being supplied with an
electric field of the normal direction (the same as one used in preparation) to effect
erasure of the record.
Comparative Example 3
[0074] A data recording medium was prepared in the same manner as in Example 3 except that
the colorant was replaced by the one used in Comparative Example 1.
[0075] The thus obtained data recording medium showed no contrast even after the application
of electric fields in the same manner as in Comparative example 2.
[0076] As described above, the data recording medium of the present invention provides a
high sensitivity and good S/N ratio and bit error rate (BER) in a recording, reproduction
and erasure system utilizing light absorption-thermal conversion of a medium comprising
a polymer liquid crystal and a light absorber. The data recording medium also shows
excellent effects, such as a good repetition durability and a good storage stability
of records because of a stable liquid crystal phase.
1. A data recording medium, comprising a recording layer which in turn comprises a polymer
liquid crystal and a colorant being soluble in said polymer liquid crystal and being
a naphthalocyanine which is inclusively represented by the following Formula (I):
wherein the symbols A, B, C and D respectively denote the following divalent group:
wherein R
1 - R
12 respectively denote a hydrogen group, a linear or branched alkyl, alkoxy or alkenyl
group having 4 to 20 carbon atoms, or a group selected from the following: -SiQ
1Q
2Q
3, -SQ
4, -COQ
5, COOQ
6, and -NQ
7Q
8, wherein Q
1 - Q
8 respectively denote a hydrogen atom, or a linear or branched alkyl or alkenyl group
having 1 to 20 carbon atoms;
M denotes Ge, Sn, transition metal, Al, Ga, In, alkaline earth metal, lanthanide element
or actinide element, or an oxide, halogenide or alkoxide thereof.
2. A medium according to claim 1, wherein said colorant is a naphthalocyanine represented
by the following formula (II):
wherein M denotes Ge, Sn, transition metal, Al, Ga, In, alkaline earth metal, lanthanide
element or actinide element; X denotes halogen atom, alkyl group, carboxyl group,
alkoxy group, ether group or alkenyl group;
Xm1 - Xm4 respectively denote halogen atom, alkyl group, sulfomoyl group, ether group or alkenyl
group; a - d are respectively a number of 0 to 4 satisfying the relationship of a+b+c+d
≥ 1.
3. A medium according to claim 1 or 2, wherein the recording layer further comprises
a metal chelate being different from the colorant according to claims 1 or 2.
4. A medium according to claim 3, wherein the metal chelate compound belongs to any one
of the classes of metal chelate compounds represented by the following formulas (1)
to (17):
wherein R
15 denotes a hydrogen atom, hydroxyl group or alkyl group capable of being connected
with another R
15; R
16 denotes alkyl group, halogen atom, hydrogen atom, nitro group, or benzo condensed
group; and M denotes a center metal of Cu, Ni, Co or Pd.
wherein R
17 denotes a hydrogen atom, hydroxyl group, alkyl group or aryl group capable of being
connected with another R
17; R
18 denotes a halogen atom, alkyl group, nitro group or condensed benzo group; and M
denotes Cu, Ni, Co or Pd.
wherein R
19 denotes an alkyl group or aryl group;
R
20 denotes a hydrogen atom, halogen atom, alkyl group, aryl group, nitro group or condensed
benzo group; and
M denotes Cu, Ni or Pd.
wherein R
21 denotes an alkyl group or aryl group;
R
22 denotes a hydrogen atom, halogen atom, alkyl group or condensed benzo group; and
M denotes Cu, Ni or Pd.
wherein R
23 denotes a hydrogen atom or alkyl group; and M denotes Cu or Ni.
wherein R
24 denotes a hydrogen atom or alkyl group; and M denotes Cu, Ni, Co or Mn.
wherein R
25 and R
26 respectively denote a substituted or non-substituted alkyl group, acyl group or aryl
group and R
25 and R
26 are capable of forming an aromatic ring in combination; M denotes Cu, Ni, Co or Pd
which can have a charge and a counter ion.
wherein R
27 denotes a sulfur atom, substituted or non-substituted amino group, oxygen atom or
thioketone group; R
28 denotes a hydrogen atom, alkyl group, halogen atom or amino group; and M denotes
Zn, Cu or Ni.
wherein R
29 denotes an alkyl group, aryl group or styryl group; and M denotes Cu, Ni or Co.
wherein R
30 denotes a hydrogen atom, halogen atom, alkyl group, acyl group or aryl group; X is
optional and may denote Cl, and M denotes Ni or Zr.
wherein R
31 denotes an alkyl group or aryl group; and M denotes Cu, Ni or Co.
wherein R
32 and R
33 respectively denote an alkyl group or aryl group; and M denotes Ni.
wherein R
34 and R
35 respectively denote an alkyl group, amino group, aryl group or furan group capable
forming an alicyclic ring in combination with each other; and
M denotes Ni.
wherein R
36 and R
37 denote a hydrogen atom, halogen atom or alkyl group; X denotes an oxygen atom or
sulfur atom; and M denotes Ni.
wherein R
38 and R
39 respectively denote a hydrogen atom, alkyl group, halogen atom or nitro group; X
denotes an oxygen atom or sulfur atom; M denotes Ni; and Y
⊕ denotes a quarternary ammonium cation.
wherein R
40 denotes an amino group; and M denotes Cu, Ni, Co or Pd.
wherein R
41 denotes a hydrogen atom, halogen atom, alkyl group, acyl group, nitro group or alkoxyl
group; and M denotes Zn, Cu, Ni or Co.
6. A medium according to claim 1, wherein the soluble colorant is used in a proportion
of 0.01 - 40 wt.-% of the polymer liquid crystal.
7. A medium according to claim 1, wherein the soluble colorant is used in a proportion
of 0.1 - 25 wt.-% of the polymer liquid crystal.
8. A medium according to claim 1, 3 or 5, wherein said polymer liquid crystal is a ferroelectric
polymer liquid crystal.
1. Datenaufzeichnungsträger, der eine Aufzeichnungsschicht umfasst, die ihrerseits einen
polymeren Flüssigkristall und ein Farbmittel umfasst, das in dem erwähnten polymeren
Flüssigkristall löslich ist und ein Naphthalocyanin ist, das zusammmenfassend durch
die folgende Formel (I) wiedergegeben wird:
worin die Symbole A, B, C und D jeweils die folgende zweiwertige Gruppe bezeichnen:
worin R
1 bis R
12 jeweils ein Wasserstoffatom, eine lineare oder verzweigte Alkyl-, Alkoxy- oder Alkenylgruppe
mit 4 bis 20 Kohlenstoffatomen oder eine Gruppe bezeichnen, die aus den folgenden
ausgewählt ist: -SiQ
1Q
2Q
3, -SQ
4, -COQ
5, -COOQ
6 und -NQ
7Q
8, worin Q
1 bis Q
8 jeweils ein Wasserstoffatom oder eine lineare oder verzweigte Alkyl- oder Alkenylgruppe
mit 1 bis 20 Kohlenstoffatomen bezeichnen; und M Ge, Sn, ein Übergangsmetall, Al,
Ga, In, ein Erdalkalimetall, ein Lanthanoidenelement oder ein Actinoidenelement oder
ein Oxid, Halogenid oder Alkoxid davon bezeichnet.
2. Datenaufzeichnungsträger nach Anspruch 1, bei dem das erwähnte Farbmittel ein Naphthalocyanin
ist, das durch die folgende Formel (II) wiedergegeben wird:
worin M Ge, Sn, ein Übergangsmetall, Al, Ga, In, ein Erdalkalimetall, ein Lanthanoidenelement
oder ein Actinoidenelement bezeichnet; X ein Halogenatom, eine Alkylgruppe, eine Carboxylgruppe,
eine Alkoxygruppe, eine Ethergruppe oder eine Alkenylgruppe bezeichnet; Xm
1 bis Xm
4 jeweils ein Halogenatom, eine Alkylgruppe, eine Sulfamoylgruppe, eine Ethergruppe
oder eine Alkenylgruppe bezeichnen und a bis d jeweils eine Zahl von 0 bis 4 bedeuten
und die Beziehung a + b + c + d ≥ 1 erfüllen.
3. Datenaufzeichnungsträger nach Anspruch 1 oder 2, bei dem die Aufzeichnungsschicht
ferner ein Metallchelat enthält, das sich von dem Farbmittel gemäß Anspruch 1 oder
2 unterscheidet.
4. Datenaufzeichnungsträger nach Anspruch 3, bei dem die Metallchelatverbindung zu irgendeiner
der Gruppen von Metallchelatverbindungen gehört, die durch die folgenden Formeln (1)
bis (17) wiedergegeben werden:
worin R
15 ein Wasserstoffatom, eine Hydroxylgruppe oder eine Alkylgruppe, die mit einem anderen
R
15 verbunden sein kann, bezeichnet; R
16 eine Alkylgruppe, ein Halogenatom, ein Wasserstoffatom, eine Nitrogruppe oder eine
kondensierte Benzogruppe bezeichnet und M ein Zentralatom, und zwar Cu, Ni, Co oder
Pd, bezeichnet;
worin R
17 ein Wasserstoffatom, eine Hydroxylgruppe, eine Alkylgruppe oder eine Arylgruppe,
die mit einem anderen R
17 verbunden sein kann, bezeichnet; R
18 ein Halogenatom, eine Alkylgruppe, eine Nitrogruppe oder eine kondensierte Benzogruppe
bezeichnet und M Cu, Ni, Co oder Pd bezeichnet;
worin R
19 eine Alkylgruppe oder eine Arylgruppe bezeichnet; R
20 ein Wasserstoffatom, ein Halogenatom, eine Alkylgruppe, eine Arylgruppe, eine Nitrogruppe
oder eine kondensierte Benzogruppe bezeichnet und M Cu, Ni oder Pd bezeichnet;
worin R
21 eine Alkylgruppe oder eine Arylgruppe bezeichnet; R
22 ein Wasserstoffatom, ein Halogenatom, eine Alkylgruppe oder eine kondensierte Benzogruppe
bezeichnet und M Cu, Ni oder Pd bezeichnet;
worin R
23 ein Wasserstoffatom oder eine Alkylgruppe bezeichnet und M Cu oder Ni bezeichnet;
worin R
24 ein Wasserstoffatom oder eine Alkylgruppe bezeichnet und M Cu, Ni, Co oder Mn bezeichnet;
worin R
25 und R
26 jeweils eine substituierte oder nichtsubstituierte Alkylgruppe, Acylgruppe oder Arylgruppe
bezeichnen und R
25 und R
26 in Kombination einen aromatischen Ring bilden können und M Cu, Ni, Co oder Pd bezeichnet,
das eine Ladung und ein Gegenion haben kann;
worin R
27 ein Schwefelatom, eine substituierte oder nichtsubstituierte Aminogruppe, ein Sauerstoffatom
oder eine Thioketongruppe bezeichnet; R
28 ein Wasserstoffatom, eine Alkylgruppe, ein Halogenatom oder eine Aminogruppe bezeichnet
und M Zn, Cu oder Ni bezeichnet;
worin R
29 eine Alkylgruppe, eine Arylgruppe oder eine Styrylgruppe bezeichnet und M Cu, Ni
oder Co bezeichnet;
worin R
30 ein Wasserstoffatom, ein Halogenatom, eine Alkylgruppe, eine Acylgruppe oder eine
Arylgruppe bezeichnet; X wahlweise ist und Cl bezeichnen kann und M Ni oder Zr bezeichnet;
worin R
31 eine Alkylgruppe oder eine Arylgruppe bezeichnet und M Cu, Ni oder Co bezeichnet;
worin R
32 und R
33 jeweils eine Alkylgruppe oder eine Arylgruppe bezeichnen und M Ni bezeichnet;
worin R
34 und R
35 jeweils eine Alkylgruppe, eine Aminogruppe, eine Arylgruppe oder eine Furangruppe
bezeichnen, die in Kombination miteinander einen alicyclischen Ring bilden können;
und M Ni bezeichnet;
worin R
36 und R
37 ein Wasserstoffatom, ein Halogenatom oder eine Alkylgruppe bezeichnen; X ein Sauerstoffatom
oder ein Schwefelatom bezeichnet und M Ni bezeichnet;
worin R
38 und R
39 jeweils ein Wasserstoffatom, eine Alkylgruppe, ein Halogenatom oder eine Nitrogruppe
bezeichnen; X ein Sauerstoffatom oder ein Schwefelatom bezeichnet; M Ni bezeichnet
und Y
⊕ ein quartäres Ammoniumkation bezeichnet;
worin R
40 eine Aminogruppe bezeichnet und M Cu, Ni, Co oder Pd bezeichnet;
worin R
41 ein Waserstoffatom, ein Halogenatom, eine Alkylgruppe, eine Acylgruppe, eine Nitrogruppe
oder eine Alkoxygruppe bezeichnet und M Zn, Cu, Ni oder Co bezeichnet.
6. Datenaufzeichnungsträger nach Anspruch 1, bei dem das lösliche Farbmittel in einem
Anteil von 0,01 bis 40 Masse% des polymeren Flüssigkristalls verwendet wird.
7. Datenaufzeichnungsträger nach Anspruch 1, bei dem das lösliche Farbmittel in einem
Anteil von 0,1 bis 25 Masse% des polymeren Flüssigkristalls verwendet wird.
8. Datenaufzeichnungsträger nach Anspruch 1, 3 oder 5, bei dem der erwähnte polymere
Flüssigkristall ein ferroelektrischer polymerer Flüssigkristall ist.
1. Support d'enregistrement de données, comprenant une couche d'enregistrement qui comprend
elle-même un cristal liquide polymère et une matière colorante soluble dans ledit
cristal liquide polymère, et consistant en une naphtalocyanine qui est représentée
inclusivement par la formule (I) suivante :
dans laquelle les symboles A, B, C et D représentent respectivement les groupes
divalents suivants :
dans lesquels R
1 à R
12 représentent respectivement un atome d'hydrogène, un groupe alkyle, alkoxy ou alcényle
linéaire ou ramifié ayant 4 à 20 atomes de carbone, ou un groupe choisi parmi les
suivants : -SiQ
1Q
2Q
33, -SQ
4, -COQ
5, COOQ
6, et -NQ
7Q
8, dans lesquels Q
1 à Q
8 représentent respectivement un atome d'hydrogène, ou un groupe alkyle ou alcényle
linéaire ou ramifié ayant 1 à 20 atomes de carbone ;
M représente Ge, Sn, un métal de transition, Al, Ga, In, un métal alcalino-terreux,
un élément faisant partie des lanthanides ou un élément faisant partie des actinides,
ou un de leurs oxydes, halogénures ou alcoolates.
2. Support suivant la revendication 1, dans lequel la matière colorante est une naphtalocyanine
représentée par la formule (II) suivante :
dans laquelle M représente Ge, Sn, un métal de transition, Al, Ga, In, un métal alcalino-terreux,
un élément faisant partie des lanthanides ou un élément faisant partie des actinides
; X représente un atome d'halogène, un groupe alkyle, un groupe carboxyle, un groupe
alkoxy, un groupe éther ou un groupe alcényle ;
Xm1 à Xm4 représentent respectivement un atome d'halogène, un groupe alkyle, un groupe sulfamoyle,
un groupe éther ou un groupe alcényle ; a à d représentent respectivement un nombre
de 0 à 4, satisfaisant la relation a + b + c + d ≥ 1.
3. Support suivant la revendication 1 ou 2, dans lequel la couche d'enregistrement comprend
en outre un chélate métallique différent de la matière colorante suivant la revendication
1 ou 2.
4. Support suivant la revendication 3, dans lequel le chélate métallique appartient à
n'importe laquelle des catégories de chélates métalliques représentés par les formules
(1) à (17) suivantes :
dans laquelle R
15 représente un atome d'hydrogène, un groupe hydroxyle ou un groupe alkyle pouvant
être connecté à un autre groupe R
15 ; R
16 représente un groupe alkyle, un atome d'halogène, un atome d'hydrogène, un groupe
nitro ou un groupe benzo condensé ; et M représente un métal central consistant en
Cu, Ni, Co ou Pd ;
dans laquelle R
17 représente un atome d'hydrogène, un groupe hydroxyle, un groupe alkyle ou un groupe
aryle pouvant être connecté à un autre groupe R
17 ; R
18 représente un atome d'halogène, un groupe alkyle, un groupe nitro ou un groupe benzo
condensé ; et M représente Cu, Ni, Co, ou Pd ;
dans laquelle R
19 représente un groupe alkyle ou un groupe aryle ; R
20 représente un atome d'hydrogène, un atome d'halogène, un groupe alkyle, un groupe
aryle, un groupe nitro ou un groupe benzo condensé ; et M représente Cu, Ni ou Pd
;
dans laquelle R
21 représente un groupe alkyle ou un groupe aryle ; R
22 représente un atome d'hydrogène, un atome d'halogène, un groupe alkyle ou un groupe
benzo condensé ; et M représente Cu, Ni ou Pd ;
dans laquelle R
23 représente un atome d'hydrogène ou un groupe alkyle ; et M représente Cu ou Ni ;
dans laquelle R
24 représente un atome d'hydrogène ou un groupe alkyle ; et M représente Cu, Ni, Co
ou Mn ;
dans laquelle R
25 et R
26 représentent respectivement un groupe alkyle substitué ou non substitué, un groupe
acyle ou un groupe aryle, et R
25 et R
26 sont capables de former un noyau aromatique en association ; M représente Cu, Ni,
Co ou Pd, qui peut porter une charge et un ion complémentaire ;
dans laquelle R
27 représente un atome de soufre, un groupe amino substitué ou non substitué, un atome
d'oxygène ou un groupe thiocétone ; R
28 représente un atome d'hydrogène, un groupe alkyle, un atome d'halogène ou un groupe
amino ; et M représente Zn, Cu ou Ni ;
dans laquelle R
29 représente un groupe alkyle, un groupe aryle ou un groupe styryle ; et M représente
Cu, Ni ou Co ;
dans laquelle R
30 représente un atome d'hydrogène, un atome d'halogène, un groupe alkyle, un groupe
acyle ou un groupe aryle ; X est facultatif et peut représenter Cl, et M représente
Ni ou Zr ;
dans laquelle R
31 représente un groupe alkyle ou un groupe aryle ; et M représente Cu, Ni ou Co ;
dans laquelle R
32 et R
33 représentent respectivement un groupe alkyle ou un groupe aryle ; et M représente
Ni ;
dans laquelle R
34 et R
35 représentent respectivement un groupe alkyle, un groupe amino, un groupe aryle ou
un groupe furanne, ces groupes étant capables de former un noyau alicyclique en association
l'un avec l'autre ; et M représente Ni ;
dans laquelle R
36 et R
37 représentent un atome d'hydrogène, un atome d'halogène ou un groupe alkyle ; X représente
un atome d'oxygène ou un atome de soufre ; et M représente Ni ;
dans laquelle R
38 et R
39 représentent respectivement un atome d'hydrogène, un groupe alkyle, un atome d'halogène
ou un groupe nitro ; X représente un atome d'oxygène ou un atome de soufre ; M représente
Ni ; et Y
⊕ représente un cation ammonium quaternaire ;
dans laquelle R
40 représente un groupe amino ; et M représente Cu, Ni, Co ou Pd ;
dans laquelle R
41 représente un atome d'hydrogène, un atome d'halogène, un groupe alkyle, un groupe
acyle, un groupe nitro ou un groupe alkoxyle ; et M représente Z, Cu, Ni ou Co.
6. Support suivant la revendication 1, dans lequel la matière colorante soluble est utilisée
en une proportion de 0,01 à 40 % en poids du cristal liquide polymère.
7. Support suivant la revendication 1, dans lequel la matière colorante soluble est utilisée
en une proportion de 0,1 à 25 % en poids du cristal liquide polymère.
8. Support suivant la revendication 1, 3 ou 5, dans lequel le cristal liquide polymère
est un cristal liquide polymère ferroélectrique.